Tissue and organ preservation solutions have been designed to: i) lengthen the time a tissue or organ may be maintained, extra-corporeally, in a viable state and ii) maximize the performance of the tissue or organ following implantation in a recipient. Examples of these solutions include: a) the Stanford University solution (see, Swanson, D. K., et al., Journal of Heart Transplantation, (1988), vol. 7, No. 6, pages 456-467); b) modified Collins solution (see, Maurer, E. J., et al., Transplantation Proceedings, (1990), vol. 22, No. 2, pages 548-550; Swanson, D. K., et al.); and c) the University of Wisconsin solution (see, Belzer, et al., U.S. Pat. No. 4,798,824, issued Jan. 17, 1989).
Each of the above mentioned tissue or organ preservation solutions exerts a different effect on: i) the physiology and metabolism, during the period of ex vivo preservation, of a candidate tissue or organ and ii) the post transplant viability of said tissue or organ. Moreover, different protocols (for cardiac preservation) have been described using these solutions including: a) warm arrest/cold ischemia, b) cold arrest/macroperfusion, c) cold arrest/microperfusion, and d) cold arrest/cold ischemia.
This first method of cardiac preservation involves arresting the heart with a warm cardioplegic solution prior to exsanguination and cold preservation. This protocol, however, is not optimal given the rapid depletion of myocardial energy stores during the “warm” period.
The second method, which involves arresting the heart with a cold preservation solution, is better but continuous perfusion of the heart with traditional preservation solutions generates oxygen free radicals which can compromise the viability of the candidate tissue or organ after transplantation.
The third method, first described in the journal Nature in 1972 in a system called “trickle perfusion,” also generates undesirable oxygen free radicals.
The fourth method, cold cardioplegic arrest of the candidate donor heart followed by immersion in a cold organ preservation solution, is currently the standard method of cardiac preservation. While this method creates a maximum six (6) hour “window of preservation”; preservation for more than four (4) hours is associated with a marked decrease in post transplantation viability.
Compounding these problems is the associated issue of organ availability. In the United States, all cardiac allografts are presently obtained from brain-dead, beating heart donors maintained on life support systems. As a result of this severely limited organ pool, 10%-40% of all cardiac transplant candidates die awaiting a new organ.
What is needed, therefore, is: i) a physiological solution that extends the amount of time a candidate organ remains viable for transplantation, and ii) methods and devices for evaluating the prospective performance of a candidate donor and/or cadaveric heart in advance of transplantation.